The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In a lower portion of a front suspension of a vehicle there are typically two main bushings that contribute to the feel of a vehicle, the ride bushing and the handling bushing, as shown in FIG. 1. The handling bushing contributes to the stiffness of the steering. The ride bushing helps to control how much wheel impact, such as when the vehicle hits a pothole, that the driver and the passenger(s) will feel. It is important to shut the travel of the bushing down to ensure that the vehicle does not have a shaky feel. It is equally important that the travel is not reduced too rapidly or else wheel impacts will feel sharp and jarring to the driver and passenger(s) riding in the vehicle.
More particularly, as also shown in FIG. 1, in a typical vehicle suspension, as the wheel moves fore-aft, the control arm link (L) will move the outer tube of the bushing, along with the inner metal of the stopper and its internal cup structure fixed thereto, in the Y-direction. With bushings, a radial stopper is used as a way of limiting the linear and/or total travel in the specified radial direction (i.e., Y direction). Radial stoppers are most commonly used in Hydroelastic™ bushings, which are available from Tenneco, Inc. of Lake Forest, Ill., due to the limited package space for the bushing. Axial and radial stoppers used with present day bushing assemblies typically consist of a rubber pad which is used to ramp up the load (in the Y direction) which restricts the travel of the bushing at a given load. However, the rubber that makes up the radial stopper is typically free to bulge on all of its sides as the bushing applies an increasing force on the stopper during its travel. This bulging of the rubber makes it difficult to ramp up the load, reduce the total travel of the bushing, and reduce strains below preset design standards for a given package size.
Conventional radial stoppers that utilize material to form a hard stop, such as plastic and/or metal, usually have limited package space but require the bushing to carry high loads. This method causes an abrupt stop or a minimal rate ramp-up which is usually poor for vehicle dynamics.
When rubber is incorporated into a conventional radial stopper, a minimum load bearing area is required to limit the strain below an acceptable level. One way of tuning the total travel with a rubber stopper is to increase the load bearing area. This is not always feasible due to a limited footprint designed in for the stopper. The other way of tuning the total travel is to make the rubber thickness of the stopper thinner. This causes a more abrupt stop which is typically not desired for vehicle dynamics.
Accordingly, with bushing assemblies having a conventional radial rubber stopper construction as described above, there is no way to reliably tune the total travel of the bushing assembly while maintaining a desired, plush/gradual rate force ramp-up for the bushing assembly.